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What is the Official AFL Player Ratings system?

Determining the AFL's best player has always been tricky. Whether it be umpires, coaches, media or fans, judgements about top players have always contained a large slice of opinion.

Now, using the most sophisticated algorithm ever applied to our game, we are assessing every single action of every player, determining the impact of that action, and providing points – either positive or negative – toward that player's rating compared to his peers.

Along with the obvious acts such as goals, marks and disposals, we've included intercepts, spoils, kicking to a contest, smothers, chasing, corralling and many other 'one-percenters' - along with where and when they occurred - to paint a complete picture of ever player's impact on a game.

And the Official AFL Player Ratings are based on a player's past 40 games, which delivers a long-term view of a player's standing within the AFL.

We have also created positional ratings, so that fans can easily determine the best ruckman, small-medium defender, key defender, midfielder, midfielder-forward, small-medium forward and key forward in the game.

In addition, we continue to monitor results, take fan feedback and consult the top experts to ensure Official AFL Player Ratings remain the most accurate statistical view of our game.

How is each player's rating worked out?

Players accrue or lose points every time they are involved in a passage of play. The score awarded to them each time they are in the play is determined by a complex algorithm formulated and refined over a number of years by Champion Data. Players accrue or lose points depending on whether they have a positive or negative impact on a passage of play.

A player's rating is determined by aggregating his points tally based on a rolling window of the previous two seasons. For example, after round six of the 2014 season, a player's rating will be based on matches from round seven of the 2012 season onwards. However, only a player's most recent 40 matches are used in the calculation of his rating. This creates a buffer for players missing matches through injury, suspension, omission or by not being involved in finals. A player's most recent 30 matches are given greater weight in determining his rating. Matches 31 through 40 are progressively reduced in weighting, from 100 per cent down to five per cent for the earliest game in the window.

PLAYER RATINGS POSITIONS EXPLAINED

Key forward

Plays predominantly as a tall marking target in the forward line

Examples: Jarryd Roughead, Jeremy Cameron, Tom Hawkins

Small-medium forward

Plays predominantly in the forward half of the ground but with more freedom than a key forward

Examples: Hayden Ballantyne, Angus Monfries, Luke Breust

Midfielder

Spends the majority of time playing on the ball or on the wing

Examples: Scott Pendlebury, Jack Redden, Andrew Gaff

Midfielder-forward

Splits time equally between the forward line and the midfield. Often lines up on the half-forward flank but plays a significant amount of time in the midfield

Examples: Robbie Gray, Dayne Zorko, Travis Varcoe

Key defenders

Plays on opposition key forwards with the primary role of nullifying his opponent

Examples: Josh Gibson, Cale Hooker, Eric Mackenzie

Small-medium defender

Plays a role on opposition small-medium forwards and usually helps create play from the backline

Examples: Grant Birchall, Michael Hibberd, Kade Kolodjashnij

Ruck

Has the primary role of competing for hit-outs at a stoppage

Examples: Ben McEvoy, Nic Naitanui, Sam Jacobs

First-year player

A player who is on an AFL list for the first time in his career

Which on-field acts contribute to a player's score?

Every time a player is involved in a passage of play he has the chance to accrue points. But rather than his score being a simple tally of his possessions, marks, tackles, hit-outs, free-kicks and scores, his performance is measured using a system called Equity Ratings. The system determines where and how a player influences a contest and whether the player's effort then results in a positive result for his team. Equity Ratings includes what coaches love to describe as "pressure acts". As a result, players are rewarded for interrupting opposition passages of play as well as setting up scores for their own team.

Players who consistently produce positive contributions are rewarded more highly than players with a high volume of stats. As an example, a 20-disposal game by Cyril Rioli, where 17 disposals are positive and only one is negative, can have the same impact as a 40-disposal game by Dane Swan, where 25 are positive and nine are negative.

Can players lose points during games?

Yes. Players can receive a negative score in a number of ways, including when they give away free kicks and also when they turn the ball over. A turnover that results in an opposition score results in the largest negative score.

How is the player ratings system different to the scoring system used in AFL Fantasy and the Champion Data player ratings?

Whereas AFL Fantasy scores simply takes into account how many times a player receives and disposes of the ball, how many scores he registers and whether he wins or gives away free kicks, Official AFL Player Ratings consider a whole range of other factors. These include where the player was on the field when he received the ball, whether the player was under pressure and whether his disposal advantaged his team or led to a score.

How many players are included on the ratings list?

Only currently listed players are on the list. For this reason, the end-of-season placing for players may be different to their placing at the start of the following year if players above them have retired or been delisted. As soon as a player makes his senior debut, he begins accumulating points toward his Official AFL Player Rating.